Product Description:

The S21GSNA-RNN5-02 is a brushless servo motor built by Pacific Scientific for the S Brushless Motors series. As a six-pole neodymium magnet unit, it converts commanded current from a digital drive into controlled rotary motion for indexing tables, pick-and-place heads, and other positioning axes in industrial automation. The compact frame also matches common stepper motor footprints, simplifying installation in machinery with limited mounting space.

Mechanical integration is based on a NEMA 23 frame, allowing the motor to bolt directly to many standard gearboxes and linear stages. Its continuous stall torque is 0.5 Nm, allowing the shaft to resist static loads without an excessive temperature rise, while a peak torque of 1.36 Nm supports rapid acceleration. The three-phase winding has a line-to-line inductance of 14.4 mH, so the drive can use relatively long current loops without instability. The phase resistance is 12.0 ohms, which determines the steady-state current draw at a given bus voltage. The G winding uses one lamination stack. Because the unit is supplied without a holding brake, an external clamp is required when a vertical load must remain stationary after motor power is removed.

The motor weighs 1.4 kg, minimizing the mass added to moving carriages. Its rotor has an inertia of 0.042 × 10⁻³ kg·m², so the drive can achieve high cycle rates with modest additional torque. A torque constant of 0.3 Nm/A RMS provides a predictable relationship between commanded current and shaft torque. The generated back EMF is 0.19 V RMS/(rad/s), providing the amplifier with electrical information that supports speed calculations during operation. Position data comes from a size 21 frameless resolver. There is no secondary feedback channel, so all commutation and servo corrections use that single sensor. The housing does not include a shaft seal; therefore, installations exposed to fluids should use an external barrier or place the motor inside a dry enclosure.